There was no game patch yesterday.

Occasionally I'll get a "patch manifest" error message, but AFAIK it generally means you're having some kind of temporary problem connecting to the game servers. If I get that error, closing and restarting the game usually helps, and if there's still a problem then rebooting the computer usually resolves it. If you get that message, it might suggest reinstalling or repairing the game, but usually that isn't necessary and it can take a long time, so it's best to just reboot and try again.

If that was indeed the message you got-- "patch manifest"-- then you can read about it by searching the forums:

https://forums.elderscrollsonline.com/en/search?Search=patch+manifest

As you can see from the search results, it's been happening since 2014, so it's not exactly unusual, although I wouldn't go so far as to call it "usual," either.

If it only happens on occasion, it's probably nothing to be worried about, especially if it goes away when you close and restart the game.

But if it starts to happen a lot, you might want to try some of the steps that ZOS has suggested for resolving it.